Direct drive electric lawn mower

ABSTRACT

A direct drive electric lawn mower includes a driving device using an outer rotor electric motor formed of a stator, a rotor, a holder base, a bottom cap and a shaft, a cutting device connected to the shaft of the driving device outside the bottom cap and rotatable with the shaft and the bottom cap to cut a lawn at an even height, and an operating device including a tubular handle connected to the driving device, an electrical connector located on one end of the tubular handle remote from the driving device, a grip affixed to the handle and a switch mounted at the tubular handle and electrically connected with the electrical connector and operable to switch on/off the outer rotor electric motor of the driving device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to lawn mower technology and more particularly, to a direct drive electric lawn mower, which uses an outer rotor electric motor to provide a large torque for rotating a cutting device to cut a lawn at an even height efficiently.

2. Description of the Related Art

The engine of a lawn mower consumes gasoline or diesel during operation. When burning gasoline or diesel during the operation of a lawn mower engine, much waste gas (such as: sulfur dioxide, carbon monoxide) will be produced to pollute the air. In order to meet environmental protection requirements, a power lawn mower may use a carbon brush motor to substitute for a gasoline or diesel engine for rotating the cutter. Because a carbon brush motor consumes city power supply or battery power supply, it does not release waste gas during operation. The carbon brushes of a carbon brush motor are electromechanical conducting devices that connect to moving parts to provide an electric current. The carbon brushes of a carbon brush motor for lawn mower run on direct current (DC). However, a carbon brush motor does not allow conduction of a high current. The limited output of a DC carbon brush motor requires a reduction gear to enhance the torque. Short service life and low performance are the drawbacks of DC carbon brush motors.

SUMMARY OF THE INVENTION

The present invention has been accomplished under the circumstances in view. It is the main object of the present invention to provide a direct drive electric lawn mower, which is environmentally friendly, and uses an outer rotor electric motor to provide a large torque for rotating a cutting device to cut a lawn at an even height efficiently.

To achieve this and other objects of the present invention, a direct drive electric lawn mower comprises a driving device, a cutting device, and an operating device. The driving device comprises an outer rotor electric motor and a connection member. The outer rotor electric motor comprises a stator, a rotor arranged around the stator, a holder base affixed to the top side of the stator and connected to the connection member, a bottom cap connected to the bottom side of the rotor, and a shaft mounted in the holder base and extending out of the bottom side of the bottom cap and rotatable with the bottom cap by the rotor. The cutting device is connected to the shaft of the driving device outside the bottom cap and rotatable with the shaft and the bottom cap to cut a lawn at an even height. The operating device comprises a tubular handle connected to the connection member of the driving device, an electrical connector located on one end of the tubular handle remote from the driving device, a grip affixed to the handle, and an on/off switch mounted at the tubular handle and electrically connected with the electrical connector and the outer rotor electric motor of the driving device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view of a direct drive electric lawn mower in accordance with a first embodiment of the present invention.

FIG. 2 is an exploded view of a part of the direct drive electric lawn mower in accordance with the first embodiment of the present invention, illustrating the relationship between the outer rotor electric motor and connection member of the driving device.

FIG. 3 is an exploded view of a part of the direct drive electric lawn mower in accordance with the first embodiment of the present invention, illustrating the relationship between the stator and holder base the outer rotor electric motor and connection member of the driving device.

FIG. 4 is an exploded, sectional elevational view of the outer rotor electric motor of the direct drive electric lawn mower in accordance with the first embodiment of the present invention.

FIG. 5 is a sectional plain view of the outer rotor electric motor of the direct drive electric lawn mower in accordance with the first embodiment of the present invention.

FIG. 6 is an exploded view of a part of the direct drive electric lawn mower in accordance with the first embodiment of the present invention, illustrating the structure of the cutting device and the relationship between the cutting device and the driving device.

FIG. 7 is an elevational view of a direct drive electric lawn mower in accordance with a second embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 1-6, a direct drive electric lawn mower in accordance with a first embodiment of the present invention is shown. The direct drive electric lawn mower comprises a driving device 1, a cutting device 2, and an operating device 3.

The driving device 1 comprises an outer rotor electric motor 11, and a connection member 12. The outer rotor electric motor 11 comprises a stator 111, which defines therein an axial center mounting hole 1111 and a first axial locating groove 1112 in the periphery of the center mounting hole 111, a rotor 112, which comprises an annular shell 1121 arranged around the stator 111, and a plurality of magnets 1122 equiangularly mounted inside the annular shell 1121 and kept in proximity to the periphery of the stator 111, a holder base 113 fastened to one side (the top side) of the stator 111 and having a center tube 1131 inserted into the axial center mounting hole 1111 of the stator 111 and a second locating groove 1132 longitudinally located on the periphery of the center tube 1131 corresponding to the first axial locating groove 1112 of the stator 111, two bearings 117 respectively mounted in opposing top and bottom ends of the center tube 1131 of the holder base 113, a wedge block 116 engaged into the first axial locating groove 1112 and the second locating groove 1132 to prohibit relative rotation between the stator 111 and the holder base 113, a bottom cap 114, which comprises a cap body 1141 attached to the opposite side (the bottom side) of the stator 111 and defining a cross-notched center hole 1143, a plurality of locating rods 1142 equiangularly and upwardly extended from the border of the cap body 1141 and respectively inserted into the inside of the annular shell 1121 of the rotor 112 between each two adjacent magnets 1122, a shaft 115 inserted through the center tube 1131 of the holder base 113 to the outside of the bottom cap 114 and coupled to the two bearings 117, a connector 118 fastened to one end (the top end) of the shaft 115 and supported on the bearing 117 at the top side of the holder base 113, and a limiter pin 119 transversely fastened to the shaft 115 and mounted in the cross-notched center hole 1143 to prohibit relative rotation between the bottom cap 114 and the shaft 115. The connection member 12 comprises a shield portion 121, a plurality of mounting through holes 1211 cut through opposing top and bottom sides of the shield portion 121, and a shank portion 122 extended from the shield portion 121.

The cutting device 2 comprises a rotary cutter 21. The rotary cutter 21 comprises a wheel 211, and at least one, for example, two ropes 212 connected to the wheel 211 at two opposite sides. Further, the wheel 211 is fastened to the bottom end of the shaft 115 outside the bottom cap 114 with fastening components 4.

The operating device 3 comprises a tubular handle 31, an electrical connector 32 located on one end, namely, the top end of the tubular handle 31, a grip 33 affixed to the handle 31, and an on/off switch 34 mounted at the tubular handle 31.

When assembling the direct drive electric lawn mower, attach the shield portion 121 of the connection member 12 to the top side of the holder base 113 of the outer rotor electric motor 11 of the driving device 1 and then affix the mounting through holes 1211 of the shield portion 121 to the holder base 113 with fastening components 4, and then press-fit the shank portion 122 of the connection member 12 into the opposite end, namely, the bottom end of the tubular handle 31 of the operating device 3 and affix them together with a fastening component 4, and then electrically connect the electrical connector 32 and the on/off switch 34 to the outer rotor electric motor 11 of the driving device 1, and then fasten the wheel 211 of the rotary cutter 21 to the bottom end of the shaft 115 of the outer rotor electric motor 11 of the driving device 1 outside the bottom cap 114 with fastening components 4. Thus, the direct drive electric lawn mower is assembled, as shown in FIG. 1. Further, he electrical connector 32 of the operating device 3 is electrically connected to a power supply device (not shown). When using the direct drive electric lawn mower, switch on the on/off switch 34 of the operating device 3 to start the outer rotor electric motor 11 of the driving device 1, causing the rotor 112 of the outer rotor electric motor 11 to rotate the bottom cap 114 and the shaft 115. At this time, the wheel 211 of the rotary cutter 21 cutting device 2 is rotated with the shaft 115 of the outer rotor electric motor 11 of the driving device 1, moving the ropes 212 of the rotary cutter 21 to cut a lawn at an even height.

Referring to FIG. 7, a direct drive electric lawn mower in accordance with a second embodiment of the present invention is shown. This second embodiment is substantially similar to the aforesaid first embodiment with the exception that the cutting device 2 in this second embodiment is formed of a blade cutter 22 that is directly affixed to the bottom end of the shaft 115 of the outer rotor electric motor 11 of the driving device 1 outside the bottom cap 114 with fastening components 4. When switched on the on/off switch 34 of the operating device 3 to start the outer rotor electric motor 11 of the driving device 1, the rotor 112 of the outer rotor electric motor 11 is driven to rotate the bottom cap 114 and the shaft 115, thereby moving the blade cutter 22 to cut a lawn at an even height. 

What the invention claimed is:
 1. A direct drive electric lawn mower, comprising: a driving device comprising an outer rotor electric motor and a connection member, said outer rotor electric motor comprising a stator, a rotor arranged around said stator, a holder base affixed to a top side of said stator and connected to said connection member, a bottom cap connected to a bottom side of said rotor, and a shaft mounted in said holder base and extending out of a bottom side of said bottom cap and rotatable with said bottom cap by said rotor; a cutting device connected to said shaft of said driving device outside said bottom cap and rotatable with said shaft and said bottom cap to cut a lawn at an even height; and an operating device comprising a tubular handle connected to said connection member of said driving device, an electrical connector located on one end of said tubular handle remote from said driving device, a grip affixed to said handle, and an on/off switch mounted at said tubular handle and electrically connected with said electrical connector and said outer rotor electric motor of said driving device.
 2. The direct drive electric lawn mower as claimed in claim 1, wherein said stator comprises an axial center mounting hole and a first axial locating groove disposed in said axial center mounting hole; said holder base of said outer rotor electric motor comprises a center tube inserted into said axial center mounting hole of said stator, a second locating groove longitudinally located on the periphery of said center tube, and a wedge block engaged into said first axial locating groove and said second locating groove.
 3. The direct drive electric lawn mower as claimed in claim 1, wherein said rotor comprises an annular shell arranged around said stator, and a plurality of magnets equiangularly mounted inside said annular shell and kept in proximity to the periphery of said stator; said bottom cap comprises a cap body attached to a bottom side of said stator, and a plurality of locating rods equiangularly and upwardly extended from the border of said cap body and respectively inserted into the inside of said annular shell between each two adjacent said magnets.
 4. The direct drive electric lawn mower as claimed in claim 1, wherein said holder base of said outer rotor electric motor comprises a center tube sleeved onto said shaft and inserted through said stator, and two bearings respectively mounted in opposing top and bottom ends of said center tube to support said shaft in said center tube.
 5. The direct drive electric lawn mower as claimed in claim 4, wherein said outer rotor electric motor further comprises a connector fastened to a top end of said shaft and supported on one said bearing at said holder base.
 6. The direct drive electric lawn mower as claimed in claim 1, wherein said bottom cap of said outer rotor electric motor comprises a cap body attached to a bottom side of said stator, said cap body defining a cross-notched center hole for the passing of said shaft; said outer rotor electric motor further comprises a limiter pin transversely fastened to said shaft and mounted in said cross-notched center hole to prohibit relative rotation between said bottom cap and said shaft.
 7. The direct drive electric lawn mower as claimed in claim 1, wherein said connection member comprises a shield portion, a plurality of mounting through holes cut through opposing top and bottom sides of said shield portion and affixed to said holder base of said outer rotor electric motor, and a shank portion extended from said shield portion and fixedly connected to said tubular handle of said operating device.
 8. The direct drive electric lawn mower as claimed in claim 1, wherein said cutting device comprises a rotary cutter, said rotary cutter comprising a wheel fixedly fastened to said shaft outside said bottom cap for rotation with said shaft, and at least one, for example, a plurality of ropes respectively connected to said wheel and movable to cut a lawn upon rotation of said wheel with said shaft.
 9. The direct drive electric lawn mower as claimed in claim 1, wherein said cutting device comprises a blade cutter directly affixed to said shaft of said outer rotor electric motor of said driving device outside said bottom cap. 